From: T E Schmitz <mailreg@numerixtechnology.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-sql@postgresql.org
Subject: Re: ORDER BY and NULLs
Date: Sun, 19 Sep 2004 18:18:37 +0100
Message-ID: <414DBF6D.8040500@numerixtechnology.de> (raw)
In-Reply-To: <19733.1095613137@sss.pgh.pa.us>
References: <011d01c49e5b$c88fdb20$2766f30a@development.greatgulfhomes.com>
<414DB1AB.5080207@sympatico.ca>
<414DB594.5000300@numerixtechnology.de>
<19733.1095613137@sss.pgh.pa.us>
Hello Tom,
Tom Lane wrote:
> T E Schmitz <mailreg@numerixtechnology.de> writes:
>
>>I read somewhere that an Index is not
>>going to improve the performance of an ORDER BY if the sort column
>>contains NULLs because NULLs aren't indexed?
>
> Whatever you were reading had it pretty badly garbled :-(
I just dug out the PostgreSQL book again because I thought I might've
garbled it:
Quote: "PostgreSQL will not index NULL values. Because an index will
never include NULL values, it cannot be used to satisfy the ORDER BY
clause of a query that returns all rows in a table."
> Btree indexes *do* store nulls, so the presence of nulls doesn't affect
Thank you for your explanations. At the moment the table has only 1300
entries and any query is responsive. I'm just planning ahead...
--
Regards/Gruß,
Tarlika Elisabeth Schmitz
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To: pgsql-sql@postgresql.org
Cc: mailreg@numerixtechnology.de, tgl@sss.pgh.pa.us
Subject: Re: ORDER BY and NULLs
In-Reply-To: <414DBF6D.8040500@numerixtechnology.de>
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